Glass compositions and fibers made therefrom

ABSTRACT

Embodiments of the present invention relate to glass compositions, glass fibers formed from such compositions, and related products. In one embodiment, a glass composition comprises 58-62 weight percent SiO 2 , 14-17 weight percent Al 2 O 3 , 14-17.5 weight percent CaO, and 6-9 weight percent MgO, wherein the amount of Na 2 O is 0.09 weight percent or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/606,493, filed Sep. 7, 2012, which is incorporated byreference in its entirety and which claims priority to U.S. ProvisionalPatent Application Ser. No. 61/532,840, filed on Sep. 9, 2011 and toU.S. Provisional Patent Application Ser. No. 61/534,041, filed on Sep.13, 2011, the entire disclosures of each being hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to glass compositions and, in particular,to glass compositions for forming fibers.

BACKGROUND

Glass fibers have been used to reinforce various polymeric resins formany years. Some commonly used glass compositions for use inreinforcement applications include the “E-glass” and “D-glass” familiesof compositions. Another commonly used glass composition is commerciallyavailable from AGY (Aiken, S.C.) under the trade name “S-2 Glass.”

In reinforcement and other applications, certain mechanical propertiesof glass fibers or of composites reinforced with glass fibers can beimportant. However, in many instances, the manufacture of glass fibershaving improved mechanical properties (e.g., higher strength, highermodulus, etc.) can result in higher costs due, for example, due toincreased batch material costs, increased manufacturing costs, or otherfactors. For example, the aforementioned “S-2 Glass” has improvedmechanical properties as compared to conventional E-glass but costssignificantly more as well as a result of substantially highertemperature and energy demands for batch-to-glass conversion meltfining, and fiber drawing. Fiber glass manufacturers continue to seekglass compositions that can be used to form glass fibers havingdesirable mechanical properties in a commercial manufacturingenvironment.

SUMMARY

Various embodiments of the present invention relate generally to glasscompositions, glass fibers formed from such glass compositions, andvarious products incorporating one or more glass fibers.

In one exemplary embodiment, a glass composition comprises 58-62 weightpercent SiO₂, 14-17 weight percent Al₂O₃, 14-17.5 weight percent CaO,and 6-9 weight percent MgO, wherein the amount of Na₂O is 0.09 weightpercent or less. A glass composition, in another exemplary embodiment,comprises 58-62 weight percent SiO₂, 14-17 weight percent Al₂O₃, 14-16weight percent CaO, 6-9 weight percent MgO, 0-1 weight percent Na₂O,0-0.2 weight percent K₂O, 0-1 weight percent Li₂O, 0-0.5 weight percentB₂O₃, 0-0.44 weight percent Fe₂O₃, 0-0.1 weight percent F₂, 0-1 weightpercent TiO₂, 0-1 weight percent ZrO₂, and 0-5 weight percent otherconstituents. In another exemplary embodiment, a glass compositioncomprises 60-62 weight percent SiO₂, 14.5-16 weight percent Al₂O₃,14.5-17.5 weight percent CaO, and 6-7.5 weight percent MgO, wherein theamount of Na₂O is 0.09 weight percent or less. A glass composition, inanother exemplary embodiment, comprises 60-62 weight percent SiO₂, 15-16weight percent Al₂O₃, 14.5-16.5 weight percent CaO, 6.5-7.5 weightpercent MgO, 0.09 weight percent or less Na₂O, 0-0.1 weight percent K₂O,0-1 weight percent Li₂O, 0-0.1 weight percent B₂O₃, 0-0.44 weightpercent Fe₂O₃, 0-0.1 weight percent F₂, 0-0.75 weight percent TiO₂,0-0.1 weight percent ZrO₂, and 0-5 weight percent other constituents.

In some embodiments, glass compositions of the present invention aresubstantially free of Na₂O. Glass compositions of the present invention,in some embodiments, are substantially free of B₂O₃. In someembodiments, the (MgO+CaO) content in glass compositions is greater thanabout 21.5 weight percent. Glass compositions, in some embodiments, canhave a CaO/MgO ratio on a weight percent basis that is greater thanabout 2.0. In some embodiments, glass compositions comprise 0-1 weightpercent K₂O. Glass compositions, in some embodiments, comprise 0.09weight percent K₂O or less. Glass compositions, in some embodiments,comprise 0-2 weight percent Li₂O. In some embodiments of glasscompositions, the (Na₂O+K₂O+Li₂O) content is less than about 1 weightpercent.

Glass compositions of the present invention, in some embodiments, arefiberizable such that the compositions can be used to form a pluralityof glass fibers. In some embodiments, glass compositions of the presentinvention can have a liquidus temperature of less than about 1250° C.Glass compositions of the present invention, in some embodiments, canhave a forming temperature of less than about 1300° C. In someembodiments, the difference between the forming temperature and theliquidus temperature of the glass compositions is at least 50° C.

Some embodiments of the present invention relate to one or more glassfibers formed from a glass composition of the present invention. In someembodiments, a glass fiber can have a Young's modulus greater than about80 GPa. A glass fiber, in some embodiments, can have a Young's modulusgreater than about 85 GPa. A glass fiber, in some embodiments, can havea Young's modulus greater than about 87 GPa.

Some embodiments of the present invention to polymeric composites. Insome embodiments, a polymeric composite comprises a polymeric material(e.g., a thermoplastic or thermosetting resin) and at least one glassfiber formed from any of the glass compositions described or disclosedherein.

These and other embodiments are discussed in greater detail in thedetailed description which follows.

DETAILED DESCRIPTION

Unless indicated to the contrary, the numerical parameters set forth inthe following specification are approximations that can vary dependingupon the desired properties sought to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all subranges subsumedtherein. For example, a stated range of “1 to 10” should be consideredto include any and all subranges between (and inclusive of) the minimumvalue of 1 and the maximum value of 10; that is, all subranges beginningwith a minimum value of 1 or more, e.g. 1 to 6.1, and ending with amaximum value of 10 or less, e.g., 5.5 to 10. Additionally, anyreference referred to as being “incorporated herein” is to be understoodas being incorporated in its entirety.

It is further noted that, as used in this specification, the singularforms “a,” “an,” and “the” include plural referents unless expressly andunequivocally limited to one referent.

The present invention relates generally to glass compositions. In oneaspect, the present invention provides glass fibers formed from glasscompositions described herein. In some embodiments, glass fibers of thepresent invention can have improved mechanical properties, such asYoung's modulus, as compared to conventional E-glass fibers.

In one embodiment, the present invention provides a glass compositioncomprising 52-67 weight percent SiO₂, 10.5-20 weight percent Al₂O₃,10.5-19 weight percent CaO, 4-14 weight percent MgO, 0-3 weight percentNa₂O, 0-1 weight percent K₂O, 0-2 weight percent Li₂O, 0-4 weightpercent B₂O₃, 0-0.44 weight percent Fe₂O₃, 0-0.5 weight percent F₂, 0-2weight percent TiO₂, 0-2 weight percent ZrO₂, and 0-5 weight percentother constituents.

Some embodiments of the present invention can be characterized by theamount of SiO₂ present in the glass compositions. SiO₂ can be present,in some embodiments, in an amount between about 52 and about 67 weightpercent. In some embodiments, SiO₂ can be present in an amount betweenabout 55 and about 67 weight percent. SiO₂ can be present in an amountbetween about 58 and about 62 weight percent in some embodiments. Insome embodiments, SiO₂ can be present in an amount between about 60 andabout 62 weight percent.

Some embodiments of the present invention can be characterized by theamount of Al₂O₃ present in the glass compositions. Al₂O₃ can be present,in some embodiments, in an amount between about 10.5 and about 20 weightpercent. In some embodiments, Al₂O₃ can be present in an amount betweenabout 11 and about 19 weight percent. Al₂O₃ can be present in an amountbetween about 14 and about 17 weight percent in some embodiments. Insome embodiments, Al₂O₃ can be present in an amount between about 14.5and about 16 weight percent. Al₂O₃ can be present in an amount betweenabout 15 and about 16 weight percent in some embodiments.

Some embodiments of the present invention can be characterized by theamount of CaO present in the glass compositions. CaO can be present, insome embodiments, in an amount between about 10.5 and about 19 weightpercent. In some embodiments, CaO can be present in an amount betweenabout 11 and about 18 weight percent. CaO can be present in an amountbetween about 14 and about 17.5 weight percent in some embodiments. Insome embodiments, CaO can be present in an amount between about 14.5 andabout 17.5 weight percent. CaO can be present in an amount between about14 and about 16 weight percent in some embodiments. In some embodiments,CaO can be present in an amount between about 14.5 and about 16.5 weightpercent.

Some embodiments of the present invention can be characterized by theamount of MgO present in the glass compositions. MgO can be present, insome embodiments, in an amount between about 4 and about 14 weightpercent. In some embodiments, MgO can be present in an amount betweenabout 4.5 and about 13 weight percent. MgO can be present in an amountbetween about 6 and about 9 weight percent in some embodiments. In someembodiments, MgO can be present in an amount between about 6 and about7.5 weight percent. MgO can be present in an amount between about 6.5and about 7.5 weight percent in some embodiments.

In some embodiments, compositions of the present invention can becharacterized by (MgO+CaO) content. The (MgO+CaO) content in someembodiments of the present invention can be greater than about 21.5weight percent. In some embodiments, the (MgO+CaO) content can begreater than about 21.7 weight percent. The (MgO+CaO) content can begreater than about 22 weight percent in some embodiments.

In some embodiments, compositions of the present invention can becharacterized by the total alkaline earth oxide (RO) content (i.e.,MgO+CaO+BaO+SrO). The RO content in some embodiments of the presentinvention can be greater than about 21.5 weight percent. In someembodiments, the RO content can be greater than about 21.7 weightpercent. The RO content can be greater than about 22 weight percent insome embodiments.

Some embodiments of the present invention can be characterized by theamount of MgO relative to CaO which can be expressed as CaO/MgO (weightpercent of CaO divided by weight percent of MgO). In some embodiments,CaO/MgO can be greater than about 2.0. The CaO/MgO ratio can be greaterthan about 2.1 in some embodiments.

Some embodiments of the present invention can be characterized by theamount of Na₂O present in the glass compositions. Na₂O can be present,in some embodiments, in an amount between about 0 and about 3 weightpercent. In some embodiments, Na₂O can be present in an amount betweenabout 0 and about 2.5 weight percent. Na₂O can be present in an amountless than about 1 weight percent in some embodiments. In someembodiments, Na₂O can be present in an amount of 0.09 weight percent orless. In some embodiments, glass compositions of the present inventioncan be substantially free of Na₂O, meaning that any Na₂O present in theglass composition would result from Na₂O being present as a traceimpurity in a batch material.

Some embodiments of the present invention can be characterized by theamount of K₂O present in the glass compositions. K₂O can be present, insome embodiments, in an amount between about 0 and about 1 weightpercent. In some embodiments, K₂O can be present in an amount less thanabout 0.2 weight percent. K₂O can be present in an amount of 0.09 weightpercent or less in some embodiments. In some embodiments, glasscompositions of the present invention can be substantially free of K₂O,meaning that any K₂O present in the glass composition would result fromK₂O being present as a trace impurity in a batch material.

Some embodiments of the present invention can be characterized by theamount of Li₂O present in the glass compositions. Li₂O can be present,in some embodiments, in an amount between about 0 and about 2 weightpercent. In some embodiments, Li₂O can be present in an amount betweenabout 0 and about 1 weight percent. Li₂O can be present in an amountless than about 0.7 weight percent in some embodiments.

In some embodiments, compositions of the present invention can becharacterized by the total alkali metal oxide (R₂O) content (i.e.,Na₂O+K₂O+Li₂O). The R₂O content in some embodiments of the presentinvention can be between about 0.1 and about 3 weight percent. In someembodiments, the R₂O content can be less than about 1.5 weight percent.The R₂O content can be less than about 1 weight percent in someembodiments. In some embodiments, the Na₂O content in the glasscomposition can be less than the K₂O content and/or the Li₂O content.

Some embodiments of the present invention can be characterized by theamount of B₂O₃ present in the glass compositions. B₂O₃ can be present,in some embodiments, in an amount between about 0 and about 4 weightpercent. In some embodiments, B₂O₃ can be present in an amount less thanabout 1 weight percent. B₂O₃ can be present, in some embodiments, in anamount less than about 0.5 weight percent. In some embodiments, glasscompositions of the present invention can be substantially free of B₂O₃,meaning that any B₂O₃ present in the glass composition would result fromB₂O₃ being present as a trace impurity in a batch material.

Some embodiments of the present invention can be characterized by theamount of Fe₂O₃ present in the glass compositions. Fe₂O₃ can be present,in some embodiments, in an amount between about 0 and about 0.44 weightpercent. In some embodiments, Fe₂O₃ can be present in an amount betweenabout 0 and about 0.4 weight percent. Fe₂O₃ can be present in an amountbetween about 0.2 and about 0.3 weight percent in some embodiments.

Some embodiments of the present invention can be characterized by theamount of F₂ present in the glass compositions. F₂ can be present, insome embodiments, in an amount between about 0 and about 0.5 weightpercent. In some embodiments, F₂ can be present in an amount betweenabout 0 and about 0.1 weight percent. F₂ can be present in an amountless than about 0.1 weight percent in some embodiments.

Some embodiments of the present invention can be characterized by theamount of TiO₂ present in the glass compositions. TiO₂ can be present,in some embodiments, in an amount between about 0 and about 2 weightpercent. In some embodiments, TiO₂ can be present in an amount betweenabout 0 and about 1 weight percent. TiO₂ can be present in an amountbetween about 0.2 and about 0.75 weight percent in some embodiments. Insome embodiments, TiO₂ can be present in an amount less than about 0.75weight percent.

Some embodiments of the present invention can be characterized by theamount of ZrO₂ present in the glass compositions. ZrO₂ can be present,in some embodiments, in an amount between about 0 and about 2 weightpercent. In some embodiments, ZrO₂ can be present in an amount betweenabout 0 and about 1 weight percent. ZrO₂ can be present in an amountless than about 0.01 weight percent in some embodiments. In someembodiments, glass compositions of the present invention can besubstantially free of ZrO₂, meaning that any ZrO₂ present in the glasscomposition would result from ZrO₂ being present as a trace impurity ina batch material.

One advantageous aspect of the invention present in some of theembodiments is reliance upon constituents that are conventional in thefiber glass industry and avoidance of substantial amounts ofconstituents whose raw material sources are costly. For this aspect ofthe invention, constituents in addition to those explicitly set forth inthe compositional definition of the glasses of the present invention maybe included even though not required, but in total amounts no greaterthan 5 weight percent. These optional constituents include melting aids,fining aids, colorants, trace impurities and other additives known tothose of skill in glassmaking. For example, no BaO is required in thecompositions of the present invention, but inclusion of minor amounts ofBaO (e.g., up to about 1 weight percent) would not be precluded.Likewise, major amounts of ZnO are not required in the presentinvention, but in some embodiments minor amounts (e.g., up to about 2.0weight percent) may be included. In those embodiments of the inventionin which optional constituents are minimized, the total of optionalconstituents is no more than 2 weight percent, or no more than 1 weightpercent. Alternatively, some embodiments of the invention can be said toconsist essentially of the named constituents.

In some embodiments, the present invention provides a glass compositioncomprising 55-67 weight percent SiO₂, 11-19 weight percent Al₂O₃, 11-18weight percent CaO, 4.5-13 weight percent MgO, 0-2.5 weight percentNa₂O, 0-1 weight percent K₂O, 0-2 weight percent Li₂O, 0-1 weightpercent B₂O₃, 0-0.44 weight percent Fe₂O₃, 0-0.1 weight percent F₂, 0-1weight percent TiO₂, 0-1 weight percent ZrO₂, and 0-5 weight percentother constituents. In some further embodiments, the amount of Na₂O canbe 0.09 weight percent or less. In some embodiments, such glasscompositions can be substantially free of Na₂O. In some furtherembodiments, the (MgO+CaO) content can be greater than about 21.5 weightpercent, greater than 21.7 weight percent in others, and greater thanabout 22 weight percent in others. The ratio of CaO to MgO or CaO/MgO,in some embodiment, can be greater than 2.0, and can be greater thanabout 2.1 in others. In some embodiments, glass compositions can besubstantially free of B₂O₃.

In some embodiments, the present invention provides a glass compositioncomprising 58-62 weight percent SiO₂, 14-17 weight percent Al₂O₃,14-17.5 weight percent CaO, 6-9 weight percent MgO, 0-1 weight percentNa₂O, 0-0.2 weight percent K₂O, 0-1 weight percent Li₂O, 0-0.5 weightpercent B₂O₃, 0-0.44 weight percent Fe₂O₃, 0-0.1 weight percent F₂, 0-1weight percent TiO₂, 0-1 weight percent ZrO₂, and 0-5 weight percentother constituents. In some further embodiments, the amount of Na₂O canbe 0.09 weight percent or less. In some embodiments, such glasscompositions can be substantially free of Na₂O. In some furtherembodiments, the (MgO+CaO) content can be greater than about 21.5 weightpercent, greater than 21.7 weight percent in others, and greater thanabout 22 weight percent in others. The ratio of CaO to MgO or CaO/MgO,in some embodiment, can be greater than 2.0, and can be greater thanabout 2.1 in others. In some embodiments, glass compositions can besubstantially free of B₂O₃.

In some embodiments, the present invention provides a glass compositioncomprising 58-62 weight percent SiO₂, 14-17 weight percent Al₂O₃, 14-16weight percent CaO, 6-9 weight percent MgO, 0-1 weight percent Na₂O,0-0.2 weight percent K₂O, 0-1 weight percent Li₂O, 0-0.5 weight percentB₂O₃, 0-0.44 weight percent Fe₂O₃, 0-0.1 weight percent F₂, 0-1 weightpercent TiO₂, 0-1 weight percent ZrO₂, and 0-5 weight percent otherconstituents. In some further embodiments, the amount of Na₂O can be0.09 weight percent or less. In some embodiments, such glasscompositions can be substantially free of Na₂O. In some furtherembodiments, the (MgO+CaO) content can be greater than about 21.5 weightpercent, greater than 21.7 weight percent in others, and greater thanabout 22 weight percent in others. The ratio of CaO to MgO or CaO/MgO,in some embodiment, can be greater than 2.0, and can be greater thanabout 2.1 in others. In some embodiments, glass compositions can besubstantially free of B₂O₃.

In some embodiments, the present invention provides a glass compositioncomprising 60-62 weight percent SiO₂, 14.5-16 weight percent Al₂O₃,14.5-17.5 weight percent CaO, 6-7.5 weight percent MgO, 0.09 weightpercent or less Na₂O, 0-0.1 weight percent K₂O, 0-1 weight percent Li₂O,0-0.1 weight percent B₂O₃, 0-0.44 weight percent Fe₂O₃, 0-0.1 weightpercent F₂, 0-0.75 weight percent TiO₂, 0-0.1 weight percent ZrO₂, and0-5 weight percent other constituents. In some further embodiments, suchglass compositions can be substantially free of Na₂O. In some furtherembodiments, the (MgO+CaO) content can be greater than about 21.5 weightpercent, greater than 21.7 weight percent in others, and greater thanabout 22 weight percent in others. The ratio of CaO to MgO or CaO/MgO,in some embodiment, can be greater than 2.0, and can be greater thanabout 2.1 in others. In some embodiments, glass compositions can besubstantially free of B₂O₃.

In some embodiments, the present invention provides a glass compositioncomprising 60-62 weight percent SiO₂, 15-16 weight percent Al₂O₃,14.5-16.5 weight percent CaO, 6.5-7.5 weight percent MgO, 0.09 weightpercent or less Na₂O, 0-0.1 weight percent K₂O, 0-1 weight percent Li₂O,0-0.1 weight percent B₂O₃, 0-0.44 weight percent Fe₂O₃, 0-0.1 weightpercent F₂, 0-0.75 weight percent TiO₂, 0-0.1 weight percent ZrO₂, and0-5 weight percent other constituents. In some further embodiments, suchglass compositions can be substantially free of Na₂O. In some furtherembodiments, the (MgO+CaO) content can be greater than about 21.5 weightpercent, greater than 21.7 weight percent in others, and greater thanabout 22 weight percent in others. The ratio of CaO to MgO or CaO/MgO,in some embodiment, can be greater than 2.0, and can be greater thanabout 2.1 in others. In some embodiments, glass compositions can besubstantially free of B₂O₃.

Glass compositions, according to some embodiments of the presentinvention are fiberizable. In some embodiments, glass compositions ofthe present invention have forming temperatures (T_(F)) of less thanabout 1300° C. As used herein, the term “forming temperature” means thetemperature at which the glass composition has a viscosity of 1000 poise(or “log 3 temperature”). In some embodiments, glass compositions of thepresent invention are fiberizable at the forming temperature. Glasscompositions according to some embodiments of the present invention haveforming temperatures between about 1200° C. and about 1300° C. In someembodiments, glass compositions of the present invention have formingtemperatures ranging from about 1240° C. to about 1280° C.

Moreover, in some embodiments, glass compositions of the presentinvention have liquidus temperatures (T_(L)) less than about 1250° C.Glass compositions, according to some embodiments of the presentinvention, have liquidus temperatures ranging from about 1200° C. toabout 1240° C.

In some embodiments, the difference between the forming temperature andthe liquidus temperature of a glass composition of the present inventionranges from about 35° C. to greater than 60° C. In some embodiments, thedifference between the forming temperature and the liquidus temperatureof a glass composition of the present invention is at least 50° C.

In some embodiments, glass compositions of the present invention have amolten density at the forming temperature ranging from 2.5 g/cm² to 2.7g/cm². In some embodiments, glass compositions of the present inventionhave molten density ranging from 2.50 g/cm² to 2.65 g/cm².

As provided herein, glass fibers can be formed from some embodiments ofthe glass compositions of the present invention. In some embodiments,glass fibers of the present invention can exhibit improved mechanicalproperties relative to glass fibers formed from E-glass. For example, insome embodiments, fibers formed from glass compositions of the presentinvention can have a Young's modulus (E) greater than about 75 GPa. Insome embodiments, glass fibers of the present invention can have aYoung's modulus greater than about 80 GPa. In some embodiments, glassfibers of the present invention can have a Young's modulus greater thanabout 85 GPa. In some embodiments, glass fibers of the present inventioncan have a Young's modulus greater than about 87 GPa. Unless otherwisestated, Young's modulus values discussed herein are determined using theprocedure set forth in the Examples section below.

In some embodiments, glass fibers of the present invention can have atensile strength greater than 3300 MPa. In some embodiments, glassfibers of the present invention can have a tensile strength greater thanabout 3600 MPa. Unless otherwise stated, tensile strength values aredetermined using the procedure set forth in the Examples section.

In some embodiments, specific strength or specific modulus of glassfibers of the present invention can be important. Specific strengthrefers to the tensile strength in N/m² divided by the specific weight inN/m³. Specific modulus refers to the Young's modules in N/m² divided bythe specific weight in N/m³. In some embodiments, glass fibers of thepresent invention can have a specific strength greater than 13×10⁴ m.Glass fibers, in some embodiments of the present invention, can have aspecific strength greater than about 14×10⁴ m. In some embodiments,glass fibers of the present invention can have a specific modulusgreater than about 3.35×10⁶ m. These values are improvements overE-glass fibers which are understood to typically have a specificstrength of 11.8×10⁴ m and a specific modulus of 3.16×10⁶ m.

Commercial glass fibers of the present invention can be prepared in theconventional manner well known in the art, by blending the raw materialsused to supply the specific oxides that form the composition of thefibers. For example, typically sand is used for SiO₂, clay for Al₂O₃,lime or limestone for CaO, and dolomite for MgO and some of the CaO.

As noted above, the glass can include other additives that are added toaid the glass melting and fiber drawing processes without adverselyaffecting glass or glass fiber mechanical properties or specificmechanical properties. It is also possible for the glass to containsmall amounts of impurities that come from batch ingredients. Forexample, sulfate (expressed as SO₃) may also be present as a refiningagent. Small amounts of impurities may also be present from rawmaterials or from contamination during the melting processes, such asSrO, BaO, Cl₂, P₂O₅, Cr₂O₃, or NiO (not limited to these particularchemical forms). Other refining agents and/or processing aids may alsobe present such as As₂O₃, MnO, MnO₂, Sb₂O₃, or SnO₂, (not limited tothese particular chemical forms). These impurities and refining agents,when present, are each typically present in amounts less than 0.5% byweight of the total glass composition. Optionally, elements from rareearth group of the Periodic Table of the Elements may be added tocompositions of the present invention, including atomic numbers 21 (Sc),39 (Y), and 57 (La) through 71 (Lu). These may serve as eitherprocessing aids or to improve the electrical, physical (thermal andoptical), mechanical, and chemical properties of the glasses. The rareearth additives may be included with regard for the original chemicalforms and oxidization states. Adding rare earth elements is consideredoptional, particularly in those embodiments of the present inventionhaving the objective of minimizing raw material cost, because they wouldincrease batch costs even at low concentrations. In any case, theircosts would typically dictate that the rare earth components (measuredas oxides), when included, be present in amounts no greater than about0.1-3.0% by weight of the total glass composition.

Glass fibers according to the various embodiments of the presentinvention can be formed using any process known in the art for formingglass fibers, and more desirably, any process known in the art forforming essentially continuous glass fibers. For example, although notlimiting herein, the glass fibers according to non-limiting embodimentsof the present invention can be formed using direct-melt orindirect-melt fiber forming methods. These methods are well known in theart and further discussion thereof is not believed to be necessary inview of the present disclosure. See, e.g., K. L. Loewenstein, TheManufacturing Technology of Continuous Glass Fibers, 3^(rd) Ed.,Elsevier, N.Y., 1993 at pages 47-48 and 117-234.

Although not limiting herein, glass fibers according to some embodimentsof the present invention can be useful in structural reinforcementapplications. In some embodiments, glass fibers of the present inventioncan be used in the reinforcement of polymers including thermoplasticsand thermosets. In some embodiments, glass fibers formed from glasscompositions of the present invention can be used in reinforcementapplications. For example, some embodiments of the present inventionhaving relatively high specific strength or relatively high specificmodulus (particularly, when compared to E-glass fibers) may be desirablein applications where there is a desire to increase mechanicalproperties or product performance while reducing the overall weight ofthe composite. Some examples of potential uses of composites accordingto some embodiments of the present invention include, withoutlimitation, wind energy (e.g., windmill blades), ballistics armor,aerospace or aviation applications (e.g., interior floors of planes),and others. For example, in some embodiments, composites comprisingglass fibers according to some embodiments of the present invention canhave a higher modulus than existing standard E-glass reinforcedcomposites, and can be useful in making a new generation of wind turbineblades and other applications driven by mechanical performance.

In various embodiments, the present invention provides a polymericcomposite comprising a polymeric material and at least one glass fiberformed from any of the glass compositions described or disclosed herein.Polymeric composites according to the various embodiments of the presentinvention can be made by any method known in the art for makingpolymeric composites. For example, in one embodiment, polymericcomposites according to the present invention can be made byimpregnating woven fabrics or non-woven fabrics or mats of glass fiberswith a polymeric material and then curing the polymeric material. Inanother embodiment, continuous glass fibers and/or chopped glass fiberscomprising glass compositions of the present invention can be disposedin the polymeric material. Depending on the identity of the polymericmaterial, the polymeric material can be cured subsequent to receivingthe continuous or chopped glass fibers.

The invention will be illustrated through the following series ofspecific embodiments. However, it will be understood by one of skill inthe art that many other embodiments are contemplated by the principlesof the invention.

EXAMPLES Examples 1-11

The glasses in these examples were made by melting mixtures of reagentgrade chemicals in powder form in 10% Rh/Pt crucibles at thetemperatures between 1500° C. and 1550° C. (2732° F.-2822° F.) for fourhours. Each batch was about 1200 grams. After the 4 hour melting period,the molten glass was poured onto a steel plate for quenching. Volatilespecies, such as fluoride and alkali oxides, were not adjusted in thebatches for their emission loss because of their low concentrations inthe glasses. The compositions in the examples represent as-batchedcompositions. Commercial ingredients were used in preparing the glasses.In the batch calculation, special raw material retention factors wereconsidered to calculate the oxides in each glass. The retention factorsare based on years of glass batch melting and oxides yield in the glassas measured. Hence, the as-batched compositions illustrated in theinvention are considered to be close to the measured compositions.

TABLE 1 1 2 3 4 5 6 7 8 9 10 11 SiO₂ 60.46 60.46 60.32 60.14 59.91 59.8560.73 60.92 60.95 60.97 61.02 Al₂O₃ 15.33 15.27 15.24 15.19 15.48 15.7015.36 15.40 15.32 15.32 15.32 CaO 14.94 14.97 14.94 14.89 15.18 15.0714.98 15.02 15.22 15.23 15.22 MgO 7.28 7.00 7.20 7.49 7.10 7.04 7.007.02 6.87 6.87 6.87 Na₂O 0.66 0.66 0.66 0.66 0.67 0.67 0.66 0.66 0.060.06 0.06 K₂O 0.09 0.09 0.09 0.09 0.10 0.10 0.09 0.10 0.11 0.09 0.11Li₂O 0.20 0.61 0.60 0.60 0.61 0.61 0.61 0.30 0.61 0.63 0.643 B₂O₃ 0 0 00 0 0 0 0 0 0 0 Fe₂O₃ 0.31 0.27 0.27 0.27 0.28 0.28 0.28 0.28 0.27 0.280.27 F₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0 0 0 TiO₂ 0.72 0.650.65 0.65 0.66 0.66 0.29 0.29 0.49 0.52 0.49 ZrO₂ 0 0.01 0.01 0.01 0.010.01 0.01 0.01 0 0 0 Other 0.1 0.02 (e.g., SO₃) MgO + CaO 22.22 21.9722.14 22.38 22.28 22.11 21.98 22.04 22.09 22.1 22.09 CaO/MgO 2.05 2.142.075 1.99 2.14 2.14 2.14 2.14 2.215 2.22 2.215 R₂O 0.95 1.36 1.35 1.351.38 1.38 1.36 1.06 0.78 0.78 .813 Properties T_(L) (° C.) 1207 12101212 1211 1208 1211 1211 1216 1213 1219 T_(F) (° C.) 1273 1249 1260 12511258 1252 1270 1280 1273 1280 T_(F) − T_(L) (° C.) 66 39 48 40 50 41 5964 60 61 Density 2.601 2.61 2.621 2.621 2.584 2.585 2.555 2.542 2.5822.65 (g/cm³) Strength 3623 3734 3537 3674 3353 3751 3696 3643 3751 (MPa)Specific 14.21 14.60 13.77 14.30 13.24 14.81 14.76 14.62 14.82 Strength(10⁴ m) Modulus 86.53 85.6 86.39 85.42 83.17 86.4 (GPa) Specific 3.393.38 3.41 3.41 3.34 3.41 Modulus (10⁶ m)Melt Properties

Melt viscosity as a function of temperature and liquidus temperaturewere determined by using ASTM Test Method C965 “Standard Practice forMeasuring Viscosity of Glass Above the Softening Point,” and C829“Standard Practices for Measurement of Liquidus Temperature of Glass bythe Gradient Furnace Method,” respectively.

Table 1 above summarizes measured liquidus temperature (T_(L)) andreference temperature of forming (T_(F)) defined by melt viscosity of1000 Poise for glass compositions of Examples 1-10. Glass compositionsof Examples 1-10 demonstrated liquidus temperatures greater than 1200°C. The glass compositions exhibited forming temperatures between 1249°C. and 1280° C. The difference between the forming temperature and theliquidus temperature (or ΔT) for these compositions ranged from 39° C.to 66° C.

Mechanical Properties

For fiber tensile strength test, fiber samples from the glasscompositions were produced from a 10Rh/90Pt single tip fiber drawingunit. Approximately, 85 grams of cullet of a given composition was fedinto the bushing melting unit and conditioned at a temperature close orequal to the 100 Poise melt viscosity for two hours. The melt wassubsequently lowered to a temperature close or equal to the 1000 Poisemelt viscosity and stabilized for one hour prior to fiber drawing. Fiberdiameter was controlled to produce an approximately 10 μm diameter fiberby controlling the speed of the fiber drawing winder. All fiber sampleswere captured in air without any contact with foreign objects. The fiberdrawing was completed in a room with a controlled humidity of between 40and 45% RH.

Fiber tensile strength was measured using a Kawabata KES-G1 (Kato TechCo. Ltd., Japan) tensile strength analyzer equipped with a Kawabata typeC load cell. Fiber samples were mounted on paper framing strips using aresin adhesive. A tensile force was applied to the fiber until failure,from which the fiber strength was determined based on the fiber diameterand breaking stress. The test was done at room temperature under thecontrolled humidity between 40-45% RH. The average values were computedbased on a sample size of 65-72 fibers for each composition.

Table 1 above reports the average tensile strengths for fibers formedfrom the compositions of Examples 1-9. Tensile strengths ranged from3353 to 3751 MPa for fibers formed from the compositions of Examples1-9. Specific strengths were calculated by dividing the tensile strengthvalues (in N/m²) by the corresponding specific weights (in N/m³). Thespecific strengths of the fibers made from the compositions of Examples1-9 ranged from 13.24-14.82×10⁴ m. For comparison, a ten micron E-glassfiber was measured as having a fiber density of 2.659 g/cm³, a tensilestrength of 3076 MPa, and a specific strength of 12.2×10⁴ m. Thus,fibers made from the compositions of Examples 1-9 have tensile strengthsthat are 9-22% higher than the tensile strength of an E-glass fiber anda specific strength improvement over the E-glass fiber of 8-21%.

Young's modulus was also measured for certain glass compositions inTable 1 using the following technique. Approximately 50 grams of glasscullet having a composition corresponding to the appropriate Example inTable 1 was re-melted in a 90Pt/10Rh crucible for two hours at a meltingtemperature defined by 100 Poise. The crucible was subsequentlytransferred into a vertical tube, electrically heated furnace. Thefurnace temperature was preset at a fiber pulling temperature close orequal to a 1000 Poise melt viscosity. The glass was equilibrated at thetemperature for one hour before fiber drawing. The top of the fiberdrawing furnace had a cover with a center hole, above which awater-cooled copper coil was mounted to regulate the fiber cooling. Asilica rod was then manually dipped into the melt through the coolingcoil, and a fiber about 1-1.5 m long was drawn out and collected. Thediameter of the fiber ranged from 100μ at one end to 1000 μm at theother end.

Elastic moduli were determined using an ultrasonic acoustic pulsetechnique (Panatherm 5010 unit from Panametrics, Inc. of Waltham, Mass.)for the fibers drawn from the glass melts. Extensional wave reflectiontime was obtained using twenty micro-second duration, 200 kHz pulses.The sample length was measured and the respective extensional wavevelocity (V_(E)) was calculated. Fiber density (ρ) was measured using aMicromeritics AccuPyc 1330 pycnometer. About 20 measurements were madefor each composition and the average Young's modulus (E) was calculatedfrom the following formula:E=V _(E) ²×ρThe modulus tester uses a wave guide with a diameter of 1 mm, which setsthe fiber diameter at the contact side with the wave guide to be aboutthe same as the wave guide diameter. In other words, the end of thefiber having a diameter of 1000 μm was connected at the contact side ofthe wave guide. Fibers with various diameters were tested for Young'smodulus and the results show that a fiber diameter from 100 to 1000 μmdoes not affect fiber modulus.

Young's modulus values ranged from 83.17 to 86.53 GPa for fibers formedfrom the compositions in Table 1. Specific modulus values werecalculated by dividing the Young's modulus values by the correspondingdensities. The specific moduli of the fibers made from the compositionsof Examples 1 and 5-9 ranged from 3.34-3.41×10⁶ m. For comparison, anE-glass fiber was measured (using the same procedure as above) as havinga fiber density of 2.602 g/cm³, a modulus of 80.54 GPa, and a specificmodulus of 3.16×10⁶ m. Thus, fibers made from the compositions ofExamples 1 and 5-9 have moduli that are 3-7% higher than the modulus ofan E-glass fiber and a specific modulus improvement over the E-glassfiber of 5-8%.

Examples 12-22

Examples 12-22 were prepared on a conventional furnace for melting glasscompositions to form fiber glass. The glass batch was made fromconventional batch materials (e.g., sand, clay, limestone, etc.).Samples of molten glass were removed from the furnace and allowed tosolidify. The composition of the glass was then determined usingcalibrated x-ray fluorescence, with the exception of the Li₂O content,which was determined by conventional wet analysis. The other propertiesreported in Table 2 below were determined using the same techniques asdescribed above in connection with Examples 1-11 (including the methodsby which the fiber samples were prepared and the diameter range of thefibers) except that the glass samples from the conventional furnace wereused as the source of glass for the fibers.

TABLE 2 12 13 14 15 16 17 18 19 20 21 22 SiO₂ 60.32 60.31 60.17 60.2560.12 60.27 60.39 60.70 60.84 60.79 60.86 Al₂O₃ 14.50 14.76 14.86 14.9815.02 15.09 15.11 15.17 15.20 15.19 15.19 CaO 17.36 16.64 16.47 16.1416.03 15.83 15.58 15.44 15.51 15.54 15.52 MgO 6.06 6.52 6.65 6.87 6.977.09 7.12 6.80 6.72 6.71 6.71 Na₂O 0.06 0.06 0.06 0.06 0.06 0.07 0.070.08 0.08 0.08 0.08 K₂O 0.08 0.08 0.08 0.08 0.08 0.09 0.09 0.09 0.090.09 0.09 Li₂O 0.00 0.00 0.00 0.00 0.51 0.54 0.62 0.67 0.70 0.71 0.70B₂O₃ 0 0 0 0 0 0 0 0 0 0 0 Fe₂O₃ 0.27 0.26 0.26 0.26 0.26 0.26 0.26 0.260.26 0.27 0.27 F₂ TiO₂ 0.48 0.48 0.47 0.47 0.47 0.47 0.46 0.45 0.45 0.450.45 ZrO₂ Other (e.g., SO₃) MgO + CaO 23.42 23.16 23.12 23.01 23.0022.92 22.70 22.24 22.23 22.25 22.23 CaO/MgO 2.86 2.55 2.48 2.35 2.302.23 2.19 2.27 2.31 2.32 2.31 R₂O 0.14 0.14 0.14 0.14 0.65 0.70 0.780.84 0.87 0.88 0.87 Properties T_(L) (° C.) 1214 1213 1213 1213 12111211 1207 1204 1203 1204 1204 T_(F) (° C.) 1270 1270 1269 1270 1269 12681268 1275 1273 1272 1270 T_(F) − T_(L) (° C.) 56 57 56 57 58 57 61 71 7068 66 Density 2.63 2.63 2.63 2.62 2.62 2.62 2.62 2.60 2.61 2.61 2.61(g/cm³) Strength 3373 3597 3632 (MPa) Specific 13.1 14.00 14.19 Strength(10⁴ m) Modulus 87.93 88.38 87.90 88.10 87.90 88.02 88.58 88.86 88.8688.82 89.11 (GPa) Specific 3.41 3.43 3.41 3.43 3.42 3.43 3.45 3.49 3.473.47 3.48 Modulus (10⁶ m)

Table 2 above reports the average tensile strengths for fibers formedfrom the compositions of Examples 12, 18, and 22. Tensile strengthsranged from 3373 to 3632 MPa. Specific strengths were calculated bydividing the tensile strength values (in N/m²) by the correspondingspecific weights (in N/m³). The specific strengths of the fibers madefrom the compositions of Examples 12, 18, and 22 ranged from13.1-14.19×10⁴ m. For comparison, a ten micron E-glass fiber wasmeasured as having a fiber density of 2.659 g/cm³, a tensile strength of3076 MPa, and a specific strength of 12.2×10⁴ m. Thus, fibers made fromthe compositions of Examples 12, 18, and 22 have tensile strengths thatare 9-18% higher than the tensile strength of an E-glass fiber and aspecific strength improvement over the E-glass fiber of 7-16%.

Young's modulus values were measured for fibers formed from thecompositions in Table 2 using the same procedure described in connectionwith Table 1. Young's modulus values ranged from 87.90 to 89.11 GPa forfibers formed from the compositions in Table 2. Specific modulus valueswere calculated by dividing the Young's modulus values by thecorresponding densities. The specific moduli of the fibers made from thecompositions of Examples 12-22 ranged from 3.41-3.49×10⁶ m. Forcomparison, an E-glass fiber was measured (using the same procedure asabove) as having a fiber density of 2.602 g/cm³, a modulus of 80.54 GPa,and a specific modulus of 3.16×10⁶ m. Thus, fibers made from thecompositions of Examples 12-22 have moduli that are 9-10.6% higher thanthe modulus of an E-glass fiber and a specific modulus improvement overthe E-glass fiber of 8-10%.

Desirable characteristics, which can be exhibited by embodiments of thepresent invention, can include, but are not limited to, the provision ofnew glass compositions that exhibit desirable properties; the provisionof new glass compositions that can be used to produce glass fibershaving desirable mechanical properties; the provision of new glasscompositions that can be used to produce glass fibers at commerciallyacceptable forming temperatures; the provision of new glass compositionsthat demonstrate desirable differences in liquidus and formingtemperatures; and others.

It is to be understood that the present description illustrates aspectsof the invention relevant to a clear understanding of the invention.Certain aspects of the invention that would be apparent to those ofordinary skill in the art and that, therefore, would not facilitate abetter understanding of the invention have not been presented in orderto simplify the present description. Although the present invention hasbeen described in connection with certain embodiments, the presentinvention is not limited to the particular embodiments disclosed, but isintended to cover modifications that are within the spirit and scope ofthe invention.

That which is claimed:
 1. A glass composition comprising: 58-62 weightpercent SiO₂; 14-17 weight percent Al₂O₃; 11-17.5 weight percent CaO;6-9 weight percent MgO; less than 1 weight percent K₂O; 0-1 weightpercent TiO₂; F₂ is present in an amount up to 0.5 weight percent; andat least one rare earth oxide in an amount between 0.1 and 3.0 weightpercent; wherein the amount of Na₂O is 0.09 weight percent or less,wherein the glass composition is substantially free of Li₂O, and whereinthe (Na₂O+K₂O+Li₂O) content is less than 1 weight percent.
 2. The glasscomposition of claim 1, wherein the glass composition is substantiallyfree of B₂O₃.
 3. The glass composition of claim 1, wherein the glasscomposition is substantially free of Na₂O.
 4. The glass composition ofclaim 1, wherein the (MgO+CaO) content is greater than 21.5 weightpercent.
 5. The glass composition of claim 1, wherein the CaO content is14-17.5 weight percent.
 6. The glass composition of claim 1, furthercomprising at least one of As₂O₃, MnO, MnO₂, Sb₂O₃, and SnO₂ in anamount greater than 0 weight percent.
 7. The glass composition of claim1, further comprising MnO or MnO₂ in an amount from greater than 0weight percent to 0.5 weight percent.
 8. The glass composition of claim1, wherein the glass composition is fiberizable, has a liquidustemperature of less than 1250° C., and has a forming temperature of lessthan 1300° C., wherein the difference between the forming temperatureand the liquidus temperature is at least 50° C.
 9. The glass compositionof claim 1, wherein the glass composition is formed at a formingtemperature less than 1280° C.
 10. A glass fiber formed from the glasscomposition of claim
 1. 11. The glass fiber of claim 10, wherein theglass fiber has a Young's modulus greater than 80 GPa.
 12. The glassfiber of claim 10, wherein the glass fiber has a Young's modulus greaterthan 85 GPa.
 13. The glass fiber of claim 10, wherein the glass fiberhas a Young's modulus greater than 87 GPa.
 14. A glass compositioncomprising: 58-62 weight percent SiO₂; 14-17 weight percent Al₂O₃;11-17.5 weight percent CaO; 6-9 weight percent MgO; less than 1 weightpercent K₂O; less than 1 weight percent Li₂O; 0-1 weight percent TiO₂;ZrO₂ is present in an amount up to 2 weight percent; F₂ is present in anamount up to 0.5 weight percent, and at least one rare earth oxide in anamount between 0.1 and 3.0 weight percent; wherein the amount of Na₂O is0.09 weight percent or less, and wherein the (Na₂O+K₂O+Li₂O) content isless than 1 weight percent.
 15. The glass composition of claim 14,wherein the glass composition is substantially free of Na₂O.
 16. Theglass composition of claim 14, wherein the (MgO+CaO) content is greaterthan 21.5 weight percent.
 17. The glass composition of claim 14, whereinthe CaO content is 14-17.5 weight percent.
 18. The glass composition ofclaim 14, wherein the SiO₂ content is 60-62 weight percent.
 19. Theglass composition of claim 14, wherein the glass composition issubstantially free of B₂O₃.
 20. The glass composition of claim 14,wherein the glass composition is fiberizable, has a liquidus temperatureof less than 1250° C., has a forming temperature of less than 1300° C.,and wherein the difference between the forming temperature and theliquidus temperature is at least 50° C.
 21. A glass fiber formed fromthe glass composition of claim
 14. 22. The glass fiber of claim 21,wherein the glass fiber has a Young's modulus greater than 80 GPa.
 23. Aglass composition comprising: 58-62 weight percent SiO₂; 14-17 weightpercent Al₂O₃; 11-17.5 weight percent CaO; 6-9 weight percent MgO; lessthan 1 weight percent K₂O; less than 1 weight percent Li₂O; 0-1 weightpercent TiO₂; F₂ is present in an amount up to 0.5 weight percent; andat least one rare earth oxide in an amount between 0.1 and 3.0 weightpercent, wherein the amount of Na₂O is 0.09 weight percent or less,wherein the (Na₂O+K₂O+Li₂O) content is less than 1 weight percent, andwherein the (MgO+CaO) content is greater than 21.5 weight percent. 24.The glass composition of claim 23, wherein the CaO content is 14-17.5weight percent.
 25. The glass composition of claim 23, wherein the SiO₂content is 60-62 weight percent.
 26. The glass composition of claim 23,wherein the glass composition is substantially free of B₂O₃.
 27. A glassfiber formed from the glass composition of claim
 23. 28. The glass fiberof claim 27, wherein the glass fiber has a Young's modulus greater than80 GPa.